1. Field of the Invention
The present invention relates to an initialization method for a plasma display panel (PDP).
2. Description of the Related Art
The PDP is a flat panel display for showing characters or images using plasma generated by gas discharge, and includes more than hundreds of thousands to millions of pixels arranged in a matrix format, in which the number of pixels are determined by the size of the PDP. The PDP is divided into a direct current (DC) PDP and an alternating current (AC) PDP according to an applied driving voltage waveforms and structures of discharge cells.
Electrodes of the DC PDP are exposed in a discharge space and the current flows in the discharge space when a voltage is applied, and therefore it is problematic to provide a resistor for current limitation. On the other hand, electrodes of the AC PCP are covered with a dielectric layer, so the current is limited because of natural formation of capacitance components and the electrodes are protected from ion impulses in the case of discharging. Therefore, the life span of the AC PDP is longer than that of the DC PDP.
Scan electrodes and sustain electrodes are formed in parallel on one side of the AC PDP, and address electrodes crossing the scan electrodes and the sustain electrodes are formed on the other side of the PDP. The sustain electrodes are formed corresponding to the scan electrodes, and a terminal of each sustain electrode is typically coupled to the other sustain electrodes in common.
FIG. 1 shows a partial perspective view of an AC PDP. The PDP includes two glass substrates 1, 6. Pairs of a scan electrode 4 and a sustain electrode 5 are formed in parallel on a first glass substrate 1, and are covered with a dielectric layer 2 and a protection film 3. A plurality of address electrodes 8 are established on a second glass substrate 6, and the address electrodes 8 are covered with an insulator layer 7. Barrier ribs 9 are formed in parallel with the address electrode 8 on the insulator layer 7 between the address electrodes 8, and phosphors 10 are formed on the surface of the insulator layer 7 and on the both sides of the barrier ribs 9. The glass substrates 1, 6 face each other with discharge spaces 11 between the glass substrates 1, 6 so that the scan electrodes 4 and the sustain electrodes 5 may respectively cross the address electrodes 8. A discharge space 11 between the address electrode 8 and a crossing part of a pair of the scan electrode 4 and the sustain electrode 5 forms a discharge cell 12.
FIG. 2 schematically shows an electrode arrangement of the AC PDP shown in FIG. 1. The electrodes of the AC PDP have an m×n matrix format. The address electrodes A1 to Am are arranged in a column direction, and n scan electrodes Y1 to Yn and sustain electrodes X1 to Xn are arranged in a row direction. The discharge cell 12 in FIG. 2 corresponds to the discharge cell 12 in FIG. 1.
In the conventional AC PDP, a frame is divided into a plurality of subfields in order to drive the PDP, and gray scales are represented by a combination of subfields.
A conventional method for driving the AC PDP has a reset period, an address period, and a sustain period represented by changes of the operation according to time. The state of each cell is initialized for properly performing an address operation in the reset period. An address voltage is applied to cells (addressed cells) to select the cells that are turned on and the cells that are turned off. Wall charges are accumulated to the cells that are turned on in the address period. Sustain pulses for discharge and display of images by the addressed cells is performed in the sustain period.
A voltage high enough to discharge the cell to be initialized is applied to each electrode in the reset period. However, the voltage is applied to generate a weak discharge for the purpose of uniformly controlling the state of the wall charges of the cells. In the reset period, the wall charges are so controlled such that no discharge is generated in the sustain period without the address period.
When the panel is turned on having no voltage applied to the electrodes of the panel, or the panel is turned on while the panel is turned off and the wall charges are not arranged properly, an insufficient discharge is generated in the few seconds when the panel is initialized.
The insufficient discharge is generated for a short time when the panel is initialized, and a lesser voltage is applied in the reset period because of brightness and reduction of a circuit cost. The insufficient discharge will be referred to as a discharge that is not maintained properly in the PDP. That is, the insufficient discharge may be generated when an address discharge is not generated properly in the address period because priming particles are lacking in a cell or the wall charge configuration is not controlled by the reset period.
The address discharge is formed in a short voltage-applying moment of 2-3 μs when a scan pulse and an address pulse are applied at the same time. The discharge is not easily performed when the priming particles are lacking in the cell. Accordingly, the rate at which insufficient discharge is generated is high when the panel that has been turned off for a long time is initialized. The insufficient discharge is generated because the state of the wall charges which are formed when the panel is turned off is not reset in the reset period even though the panel is immediately turned on, when the state of the wall charges is not predictable when the panel is turned off.
Conventionally, an initialization waveform for alternately applying high voltages have been used for the purpose of eliminating the insufficient discharge. This typically requires an additional power source of circuit which increases costs. Therefore, need still exists for an improved approach to eliminate insufficient discharge upon start-up of a PDP.